1. Prior Art
The millimeter-wave radio-frequency band typically spans 30 to 300 GHz. Since RF (radio frequency bands (<10 GHz) are getting crowded by wireless applications, millimeter-wave (mm-wave) bands (>10 GHz) are becoming more popular. In USA, the 60 GHz mm-wave band is unlicensed and has a large usable bandwidth of 7 GHz. It is being proposed for mm-wave short-range high-data-rate systems. Mm-wave wireless systems typically have transmitter and receiver circuitry, collectively called a transceiver. The transceiver is connected to antennas for communicating with another transceiver. The antenna transmits and receives electromagnetic waves through free space, thereby facilitating communication between two different transceivers. Heretofore the art recognized two approaches for implementing a transceiver and antenna combination for the 60 GHz mm-wave band.
The first approach is shown in FIG. 1, which shows a top view of a typical mm-wave module. A semiconductor chip 101 is placed on an electrically conductive paddle or flat metallic surface 104. The paddle, a part of package 103, is soldered onto a printed circuit board (PCB) 102. A paddle is a flat metallic surface usually in the middle of the package.
The chip contains transmitter and receiver circuits. Duplexer 109 separates the transmit signal from receive signal. In the transmit section is power-amplifier 110 and up-converter 111; up-converter translates the low frequency to high frequency. The receive section has a low-noise-amplifier 114 and a down-converter 115; down-converter translates the high frequency to low frequency. Interconnection 113 connects a metallic pad 112 on the chip to a pin 105 of the package. The interconnection carries the signals between the board and the duplexer on the chip. Package pin 105 is connected to traces or metallic transmission lines 115 on the board. If required, a balun 106, that converts balanced signal to unbalanced signal or vice-versa, may be provided. A balanced signal is a pair of signals with opposite polarity while an unbalanced signal is a signal with one polarity. Board-antenna 107 is fed by the balanced output from the balun. The antenna radiates electromagnetic-waves 116 in order to communicate with another mm-wave module.
This type of mm-wave module exploits the properties of the PCB for making a low-loss antenna. Many modern-day transceiver modules (such as those used in cell phones, automotive radars, and satellite communications) are made in this manner. However, interconnection 103 at the mm-wave frequency has very high parasitics such as unwanted inductance, capacitance, and resistance; thus this approach is difficult to use beyond 30 GHz. In addition, the size of the module is large. This first approach is explained in more detail in, “A Low-Power Fully Integrated 60 GHz Transceiver System with OOK Modulation and On-Board Antenna Assembly”, J. Lee, Y. Huang, Y. Chen, H. Lu, C. Chang, ISSCC Conference Proceedings, San Francisco, 2009.
The second, alternative approach integrates the antenna and the chip and avoids the above difficulty has been proposed. The second approach is shown in FIG. 2. An on-chip-antenna 201 is included in the chip, which contains the transmitter and receiver circuits. This approach has no antenna on the board and no transition from board to chip; therefore, it has a smaller board size compared to the circuit of FIG. 1. However, it has a larger chip size. A planar antenna 201 is designed such that it is in resonance at the frequency of interest. Resonance occurs when the antenna radiates the highest energy. This type of integrated approach leads to a compact millimeter-wave transceiver module. It also reduces the package-to-board transition uncertainties and thereby helps reduce cost. This type of approach can be seen in the following three published articles: (1) “On the design of 60 GHz integrated antennas on 0.13 um SOI technology”, Barakat, M. H.; Ndagijimana, F.; Delaveaud, C. IEEE International SOI Conference Proceedings, 2007, pp. 117-118; (2) “Apparatus and methods for constructing antennas using vias as radiating elements formed in a substrate” U.S. Pat. No. 7,444,734, Nov. 4, 2008; and (3) “Antenna-integrated microwave-millimeter-wave module”, Sakota, Naoki; Yamada, Atsushi; Kitaoka, Koki, U.S. Pat. No. 6,388,623, May 14, 2002.
The prior-art circuits discussed have a number of drawbacks at millimeter waves. The approach of FIG. 1 will have low losses if the interconnections are well controlled and the boards are of good quality. However this increases manufacturing cost. In the approach of FIG. 2, the planar antenna requires relatively large chip area; hence the cost of the chip increases. Moreover, the efficiency of this on-chip antenna is poor at mm-waves because the substrate of the chip is thin and lossy. As a result, a significant amount of signal is lost on the chip.
Thus we have found that heretofore there has not been any available low-loss and inexpensive mm-wave antenna that can be integrated easily with the transceiver.
2. Advantages
Accordingly one or more aspects of the present system has the following advantages: The chip size is reduced, thereby reducing manufacturing cost. The interconnections can have air as surrounding medium; thus, the radiation can be efficient. It does not require any additional manufacturing steps; the regular bonding procedure used for interconnections is sufficient to make the antennas. In addition, the interconnection goes to either paddle or package pin and thus does not require any additional components and is easy to implement. This approach eliminates the parasitics and uncertainties that are present in the chip-to-board transitions. Antenna arrays can be easily made by using multiple interconnections. This greatly reduces chip and module size for phase array systems; thereby, significantly decreasing the cost. Further advantages of various embodiments and aspects will be apparent from the ensuing description and drawings.